Presence, broadly defined as the ability of a communications infrastructure to both track and disseminate a variety of dynamic attributes of individuals or objects, is rapidly becoming a key component of converged network applications in both telephone company provider and enterprise environments. Presence has rapidly evolved from its roots in instant messaging status (e.g., “buddy” status) to become a standard event mechanism for aggregating context about individuals, devices, and abstract entities (e.g., meetings, activities, and location coordinates).
Currently, the Session Initiation Protocol for Instant Messaging and Presence Leveraging Extensions (SIP/SIMPLE) based presence architecture has been standardized and is a key component in, for example, the 3rd Generation Partnership Project (3GPP) IP Multimedia Subsystem architecture (IMS).
It is known that applications often want to use a publish/subscribe model for data, as such a model provides timely information updates, and provides users with an interactive experience without the overhead of polling.
SIP provides an extension for event notification (see B. Roach, RFC 3265: Session Initiation Protocol (SIP)-Specific Event Notification, the disclosure of which is incorporated by reference herein) and publication (see A, Niemi, RFC 3903: Session Initiation Protocol (SIP) Extension for Event State Publication, the disclosure of which is incorporated by reference herein), collectively referred to as presence.